The invention relates to a device for controlling the temperature, in particular for cooling, of an LED lamp or LED modules of an LED lamp, wherein the device comprises a supply line for feeding a fluid and multiple heat exchangers connected to the supply line, wherein multiple LEDs are arranged on each heat exchanger and are coupled to the heat exchanger with respect to heat transfer, so that the fluid can control the temperature, in particular cool, the LED lamp or the LED modules. The invention also relates to a method for controlling the temperature, in particular cooling, of an LED lamp or at least two LED modules of an LED lamp, using such a device and to a method for curing of a light-cured pipe using such a device.
For light-cured pipe rehabilitation, mercury vapor discharge lamps have been used successfully for approximately 20 years. These usually require no cooling. For the curing of pipe liners having small pipe diameters in the range of household connections (DN 300-DN 50, typically DN 160) there are significant restrictions for the traditionally used UV lamp technology (gas discharge lamps) with respect to the achievable minimum dimensions (diameter and length) of the lamps. The requirement of a mechanically robust holder and protective device for the bulb lamps also involves disadvantages, because these protective elements cause shadows that are significant, in particular for small pipe diameters.
For curing a light-cured pipe liner in the field of pipe rehabilitation, in particular in the range of household connections for pipes having small diameters (less than or equal to DN 300), a compact, powerful lamp is required that is cylindrical, if possible.
Due to their small geometrical dimensions and usually high optical outputs in the range of 100 W and their potentially good energy efficiency, light emitting diodes (LEDs) are suitable radiation sources for realizing small, powerful special lamps for UV curing applications, in particular in the field of trenchless pipe rehabilitation. They allow the realization of compact, efficient light sources, which can be adapted to the optical and geometrical requirements of the materials to be cured. In addition, LEDs require no wait time for achieving their full operating power, because they can be switched quickly (in the range of milliseconds or even shorter). LEDs also emit in narrow spectral ranges with half value widths of typically 10-40 nm, so that no infrared radiation is emitted by UV-LEDs and blue LEDs. Therefore, thermal dissociation of the polymers to be cross-linked can be avoided.
The combination of the usually minimal available space for the lamp of a curing device for pipe rehabilitation and the required high power densities represents a great challenge for the structure and the function of a cooling body of such an LED lamp. This applies especially when several of these LED lamps must be operated one after the other in a pipe and good movement along curves in pipes having bends is desired.
The basic use of LEDs for pipe rehabilitation is described in International patent application Publication No. WO 2005/103121 A1. The use of LEDs for the UV curing of pipe liners is also described in European patent application publication EP 1 959 183 A1, Japanese patent application publication (Kokai) JP 2008-175381 A and International patent application Publication No. WO 2008/101499 A1. LED curing systems for pipe rehabilitation are described there.
These LED lamps, which have high power densities and are used as curing devices for pipe rehabilitation, often require very efficient cooling that prevents a degraded function due to overheating of their components. Such narrow LED lamps, which have linear constructions and are used, for example, in pipes or other environments that are tightly limited in terms of space, always have the problem that there is little space for additional parts used for cooling the LED lamps or LED modules of the LED lamps. The same problem also occurs in narrow curing devices, which have linear constructions and in which the parts must be heated in the narrow space to an operating temperature in order to guarantee a reliable functioning of the parts, for example LED lasers.
For a material to be cured by light-initiated polymerization, intensities from a few mW/cm2 up to a few 10 W/cm2 are typically required, which explains the previously mentioned required optical outputs of the LED lamps. Because the efficiency and the service life of LEDs (ratio of optical output power and the electrical operating power) are inversely proportional to the operating temperature of the LEDs, good cooling of the LEDs is required.
To be able to control the temperature of, that is cool or heat, the parts, heat must be fed to these parts or heat must be conducted away from these parts through the narrow, hose-shaped construction. As the medium for transporting the heat energy, fluids, for example air or water, are preferred.
An operation of the heat exchangers or cooling bodies in series can be technically useful, because the supply and return of a cylindrical heat exchanger/cooling body can be easily attached to opposite ends. The fluid/medium flows through the supply into the cooling body, flows through this cooling body in the axial direction, and leaves the cooling body on the opposite end through a return connection. The supply of the next cooling body in the series is then connected to the return of the preceding cooling body and the series connection is realized in this way.
This connection, however, causes a disadvantageous, sequentially increasing advance temperature of the heat exchangers/cooling bodies that carry a flow of the cooling medium downstream and thus a lower efficiency and service life of these modules, in particular the final module that has the highest operating temperature. Increasing the flow rate of the coolant is one possibility for reducing this effect. However, this is also associated with an increased pressure drop whose compensation requires either an increase in the operating pressure, which places a higher load on the heat exchanger/cooling body, or an increase in the line cross section, which is often not possible due to the tight space relationships and the higher resulting weight of the system.
From the publication WO 2008/101499 A1, a device according to the class for controlling the temperature of an LED lamp having a linear construction or LED modules of an LED lamp is known. In the interior, the device comprises a supply line in the form of a pipe, which carries a flow of air, in order to cool LEDs arranged on the lateral surface of the pipe with the air flow. In the supply line there are openings through which the air flow can escape outwards into a pipe to be rehabilitated. A return line for returning the heated air flow is not provided.
Here, it is a disadvantage that a liquid fluid, such as water, cannot be used, because water, if it came into contact with the LEDs on the outside, could destroy these parts. Liquid fluids, however, can absorb heat significantly more efficiently than gaseous fluids. The fluid also heats up as it passes each device module, so that the temperature of the front LED modules is more strongly controlled or cooled than the rear LED modules. This cooling system involves a serial connection of the heat exchangers arranged one after the other (serial flow of fluid cooling media). This leads, for example, to service lives of different lengths for the LEDs in the different LED modules.